This will allow you generate a filter list based on live registry data.
(You can also use a regular 'whois' client against filtergen.dan.me.uk to get the same output)

Options:	Enable Debug Mode Generate IPv6 Filter Generate cisco ios-xr juniper force10 mikrotik prefix-list called       Permit up-to prefix size: / (CIDR size, e.g. 24 or 64)
Data Source:	RIPE RADB APNIC
AS-SET to Query:

Output from Filter List Generator:

%
% Filter List Generator
% Copyright(c) 2020, Daniel Austin MBCS
%
% usage:
%   [-D] [-6] [-RIPE | -RADB | -APNIC] [-f filtername -t filtertype [-upto N]] as-set
%
% -D for DEBUG mode (shows working calculations)
% -6 for IPv6 filter generation
% -RIPE for whois.ripe.net lookups
% -RADB for whois.radb.net lookups
% -APNIC for whois.apnic.net lookups
% -f will generate a cisco-style filterlist called 'filtername' (use -t filtertype as follows)
%      cisco (default)
%      iox-xr
%      juniper (basic support)
%      force10
%      mikrotik
% Additionally, if using -f/-t you may specify -upto N where N is the prefix size to permit up-to
%
% Using whois.radb.net for lookups
% Generating filter list for 'AS14618'
100.24.0.0/13
103.126.232.0/24
103.136.10.0/24
103.143.45.0/24
103.145.182.0/24
103.145.192.0/24
103.147.71.0/24
103.211.172.0/24
103.226.68.0/22
103.226.68.0/23
103.226.68.0/24
103.226.69.0/24
103.226.70.0/23
103.226.70.0/24
103.226.71.0/24
103.229.8.0/24
103.238.156.0/23
103.43.38.0/23
103.70.20.0/22
103.85.213.0/24
104.171.199.0/24
104.193.187.0/24
107.20.0.0/16
107.21.0.0/18
107.21.128.0/17
107.21.64.0/18
107.22.0.0/16
107.23.0.0/17
107.23.128.0/17
109.95.191.0/24
13.248.108.0/24
130.137.170.0/24
130.137.82.0/24
130.137.89.0/24
130.50.125.0/24
131.226.191.0/24
136.184.224.0/24
136.184.225.0/24
137.83.194.0/24
137.83.200.0/24
137.83.201.0/24
137.83.206.0/23
137.83.251.0/24
139.180.17.0/24
139.180.244.0/23
139.60.0.0/24
139.60.1.0/24
139.60.3.0/24
142.0.188.0/24
142.0.191.0/24
142.202.204.0/24
142.202.42.0/24
142.54.38.0/24
142.54.39.0/24
142.54.41.0/24
146.133.127.0/24
147.160.167.0/24
148.5.72.0/24
15.177.0.0/21
15.177.64.0/23
15.193.6.0/24
155.46.135.0/24
158.247.16.0/20
161.38.192.0/22
162.215.224.0/23
162.221.182.0/24
162.221.183.0/24
162.247.160.0/24
162.247.162.0/24
163.253.46.0/24
164.153.128.0/24
164.153.129.0/24
168.149.240.0/24
168.149.241.0/24
168.149.246.0/24
168.151.30.0/24
168.245.155.0/24
172.103.40.0/24
173.195.208.0/24
173.195.209.0/24
173.195.210.0/24
173.195.211.0/24
173.199.16.0/24
173.213.62.0/24
173.213.63.0/24
173.244.38.0/24
174.129.0.0/16
174.34.245.0/24
176.110.104.0/24
18.204.0.0/14
18.208.0.0/13
18.232.0.0/14
184.72.128.0/17
184.72.64.0/19
184.72.96.0/19
184.73.0.0/16
185.127.28.0/24
185.195.0.0/22
185.211.50.0/24
185.48.120.0/22
188.172.137.0/24
188.172.138.0/24
192.111.4.0/24
192.146.118.0/24
192.149.210.0/24
192.158.25.0/24
192.159.123.0/24
192.161.148.0/24
192.161.149.0/24
192.161.150.0/24
192.184.72.0/24
192.184.73.0/24
192.188.81.0/24
192.225.212.0/24
192.225.215.0/24
192.225.217.0/24
192.225.218.0/24
192.225.219.0/24
192.225.223.0/24
192.92.97.0/24
193.16.22.0/23
194.135.119.0/24
194.42.104.0/24
194.42.105.0/24
194.42.96.0/24
194.42.97.0/24
195.82.97.0/24
198.136.165.0/24
198.17.127.0/24
198.176.127.0/24
198.177.255.0/24
198.178.114.0/24
198.178.115.0/24
199.188.156.0/24
199.19.192.0/24
199.201.127.0/24
199.30.176.0/24
199.30.183.0/24
199.47.128.0/24
199.47.129.0/24
199.91.149.0/24
202.52.43.0/24
202.8.25.0/24
202.93.4.0/23
202.93.4.0/24
202.93.5.0/24
203.119.92.0/23
203.119.92.0/24
203.119.93.0/24
204.153.219.0/24
204.236.192.0/18
204.236.224.0/19
204.75.189.0/24
204.8.28.0/24
204.8.29.0/24
204.8.30.0/24
204.8.31.0/24
205.157.216.0/24
205.167.215.0/24
205.201.40.0/24
205.220.189.0/24
206.130.43.0/24
206.190.220.0/24
207.64.134.0/23
208.70.209.0/24
208.71.23.0/24
208.75.220.0/22
208.78.4.0/23
208.78.6.0/24
208.78.7.0/24
208.79.45.0/24
208.79.47.0/24
208.80.202.0/23
208.84.160.0/24
208.88.208.0/24
208.93.103.0/24
209.94.74.0/24
213.156.160.0/19
216.115.21.0/24
216.115.22.0/24
216.182.224.0/20
216.182.224.0/21
216.182.232.0/21
216.182.232.0/22
216.182.238.0/23
23.131.144.0/24
23.133.224.0/24
23.136.176.0/24
23.141.96.0/24
23.166.224.0/24
23.20.0.0/14
23.20.0.0/15
23.22.0.0/15
23.249.216.0/24
23.249.217.0/24
23.249.221.0/24
3.208.0.0/12
3.224.0.0/12
3.80.0.0/12
34.192.0.0/12
34.224.0.0/12
35.153.0.0/16
35.168.0.0/13
44.192.0.0/11
45.112.120.0/22
45.112.120.0/24
45.136.240.0/24
45.136.241.0/24
45.136.242.0/24
45.159.120.0/24
45.223.13.0/24
45.250.63.0/24
45.250.72.0/22
45.250.72.0/23
45.250.72.0/24
45.250.73.0/24
45.250.74.0/23
45.250.74.0/24
45.250.75.0/24
45.93.188.0/24
46.174.136.0/22
46.51.208.0/22
50.112.0.0/16
50.16.0.0/14
50.16.0.0/16
50.16.245.0/24
50.16.252.0/22
50.17.0.0/16
50.19.0.0/17
50.19.128.0/17
52.0.0.0/15
52.10.0.0/15
52.12.0.0/15
52.128.40.0/24
52.128.41.0/24
52.128.42.0/24
52.128.43.0/24
52.13.252.0/23
52.16.0.0/15
52.18.0.0/15
52.192.0.0/15
52.2.0.0/15
52.20.0.0/14
52.200.0.0/13
52.24.0.0/14
52.28.0.0/16
52.29.0.0/16
52.30.0.0/15
52.32.0.0/14
52.4.0.0/14
52.44.0.0/15
52.48.0.0/14
52.52.0.0/15
52.54.0.0/15
52.58.0.0/15
52.62.0.0/15
52.64.0.0/17
52.64.128.0/17
52.65.0.0/16
52.68.0.0/15
52.70.0.0/15
52.72.0.0/15
52.74.0.0/16
52.76.0.0/17
52.76.128.0/17
52.77.0.0/16
52.8.0.0/16
52.86.0.0/15
52.88.0.0/15
52.9.0.0/16
52.90.0.0/15
52.95.240.0/24
52.95.241.0/24
52.95.242.0/24
52.95.243.0/24
52.95.244.0/24
52.95.245.0/24
52.95.246.0/24
52.95.247.0/24
52.95.248.0/24
52.95.30.0/23
52.95.52.0/22
54.144.0.0/14
54.148.0.0/15
54.150.0.0/16
54.151.0.0/17
54.151.128.0/17
54.152.0.0/16
54.153.0.0/17
54.153.128.0/17
54.154.0.0/16
54.155.0.0/16
54.156.0.0/14
54.160.0.0/14
54.164.0.0/15
54.166.0.0/15
54.168.0.0/16
54.169.0.0/17
54.169.128.0/17
54.170.0.0/16
54.171.0.0/16
54.172.0.0/15
54.174.0.0/15
54.176.0.0/15
54.179.128.0/18
54.179.192.0/18
54.183.0.0/17
54.183.128.0/17
54.184.0.0/15
54.186.0.0/15
54.188.0.0/15
54.190.0.0/16
54.191.0.0/16
54.193.0.0/17
54.193.128.0/17
54.194.0.0/16
54.195.0.0/16
54.196.0.0/15
54.198.0.0/16
54.199.0.0/17
54.199.128.0/17
54.200.0.0/15
54.202.0.0/15
54.204.0.0/15
54.206.0.0/17
54.206.128.0/17
54.207.0.0/17
54.207.128.0/17
54.208.0.0/15
54.210.0.0/16
54.211.0.0/16
54.212.0.0/16
54.213.0.0/16
54.214.0.0/17
54.214.128.0/17
54.215.0.0/17
54.215.128.0/18
54.215.192.0/18
54.216.0.0/15
54.218.0.0/17
54.218.128.0/17
54.219.0.0/17
54.219.128.0/18
54.219.192.0/18
54.220.0.0/16
54.221.0.0/16
54.224.0.0/15
54.226.0.0/15
54.228.0.0/16
54.229.0.0/17
54.229.128.0/17
54.232.128.0/18
54.232.192.0/18
54.233.128.0/17
54.233.64.0/18
54.234.0.0/15
54.236.0.0/18
54.236.128.0/17
54.236.64.0/18
54.237.0.0/16
54.238.0.0/17
54.238.128.0/17
54.240.16.0/24
54.240.24.0/22
54.240.30.0/23
54.240.32.0/20
54.240.48.0/23
54.240.8.0/21
54.241.160.0/19
54.241.192.0/18
54.242.0.0/15
54.244.128.0/17
54.244.64.0/18
54.249.128.0/17
54.249.64.0/18
54.250.0.0/17
54.250.128.0/18
54.250.192.0/18
54.253.0.0/17
54.253.128.0/17
54.254.0.0/17
54.254.128.0/17
54.255.0.0/17
54.255.128.0/17
54.64.0.0/15
54.66.0.0/17
54.66.128.0/17
54.67.0.0/17
54.68.0.0/15
54.70.0.0/15
54.72.0.0/16
54.73.0.0/16
54.74.0.0/15
54.76.0.0/15
54.78.0.0/16
54.79.0.0/17
54.79.128.0/17
54.80.0.0/14
54.84.0.0/15
54.86.0.0/16
54.87.0.0/16
54.88.0.0/16
54.89.0.0/16
54.90.0.0/15
54.92.0.0/17
54.92.128.0/17
54.93.0.0/16
54.93.0.0/19
54.93.128.0/17
54.93.32.0/19
54.93.64.0/18
54.94.0.0/17
54.94.128.0/18
54.94.192.0/18
54.95.0.0/17
54.95.128.0/17
64.238.3.0/24
64.238.7.0/24
64.252.64.0/24
64.45.128.0/24
64.45.132.0/24
64.57.14.0/24
64.57.15.0/24
64.57.9.0/24
64.66.45.0/24
64.71.238.0/24
66.59.61.0/24
66.59.62.0/24
67.202.0.0/18
67.226.221.0/24
68.64.4.0/24
69.2.101.0/24
69.59.249.0/24
69.64.150.0/24
69.72.40.0/24
69.72.41.0/24
69.72.42.0/24
69.72.43.0/24
72.13.120.0/24
72.13.123.0/24
72.13.78.0/24
72.13.79.0/24
72.44.32.0/19
72.52.62.0/24
74.112.132.0/24
74.112.133.0/24
74.116.144.0/24
74.122.241.0/24
74.221.131.0/24
75.101.128.0/17
76.223.191.0/24
76.76.17.0/24
82.115.214.0/24
85.115.38.0/24
89.251.12.0/24
89.251.13.0/24
91.197.32.0/24
91.213.81.0/24
93.191.219.0/24
98.142.176.0/24
99.77.128.0/24
99.77.129.0/24
99.77.191.0/24
99.77.254.0/24
% end of filter list for 'AS14618' (464 prefixes found) 
% took 1.19 secs for query (0.99 secs of connection time)
% used 1 connections -- 1400 lines of whois data parsed